Developmental auditory deprivation in one ear impairs brainstem binaural processing and reduces spatial hearing acuity.

Early sensory experience can exert lasting perceptual consequences. For example, a brief period of auditory deprivation early in life can lead to persistent spatial hearing deficits. Some forms of hearing loss (i.

Variation in head and pinna morphology of preserved Peromyscus spp. specimens and implications for auditory function.

The physical characteristics of an animal's head and pinna mark the beginning of auditory communication. Auditory communication is broadly achieved by receiving sounds from the environment and plays a vital role in an animal's ability to perceive and localize sounds. Natural history museums and collections, along with their vast repositories of specimens, provide a unique resource for examining how the variability in both the size and shape of the head and pinna causes variability in the detection of acoustic signals across species.

Spatial hearing and temporal processing ability of the Mongolian gerbil ( ) measured using prepulse inhibition of acoustic startle.

The Mongolian gerbil is a common model organism for studying the neural and behavioral mechanisms of binaural and spatial hearing, largely because of its ability to hear lower frequencies than other rodents and thus utilize both interaural time and level difference cues for sound localization. Prior spatial hearing studies in gerbils have relied on operant conditioning paradigms, requiring large amounts of time-consuming training and testing on multiple different tasks needed to make a comprehensive assessment of spatial hearing ability (including temporal processing, spatial acuity and spatial unmasking). This limits the ability of researchers to thoroughly assess behavioral performance in individual animals.

Towards improved measurements of bone conduction auditory brainstem responses in infants and adults: mitigation of stimulus artefact.

Objective: To reduce the amplitude of stimulus artefacts present in bone conduction auditory brainstem response (BC ABR) measurements.

Design: Electromagnetic shielding was applied to the surface of a clinical BC transducer. A foam pad was also placed on the shielded mastoid-contacting plate of the transducer.

Frequency dependence and harmonic distortion of stapes displacement and intracochlear pressure in response to very high level sounds.

Previous reports have suggested that intracochlear pressures (P) measured at the base of the cochlea increase directly proportionally with stapes displacement (D) in response to moderately high (<130 dB SPL) level sounds. Consistent with this assumption, we have reported that for low frequency sounds (<1 kHz), stapes displacement and intracochlear pressures increase linearly with sound pressure level (SPL) for moderately high levels (<130 dB SPL), but saturate at higher exposure levels (>130 dB SPL). However, the magnitudes of each response were found to be frequency dependent, thus the relationship between D and P may vary at higher frequencies or higher levels.

Degradation in Binaural and Spatial Hearing, and Auditory Temporal Processing Abilities, as a Function of Aging.

Objectives: Sensorineural hearing loss is common with advancing age, but even with normal or near-normal hearing in older persons, performance deficits are often seen for suprathreshold listening tasks such as understanding speech in background noise or localizing sound direction. This suggests there is also a more central source of the problem. Objectives of this study were to examine as a function of age (young adult to septuagenarian) performance on: 1) a spatial acuity task examining localization ability, and a spatial speech-in-noise (SSIN) recognition task, both measured in a hemi-anechoic sound field using a circular horizontal-plane loudspeaker array, and 2) a suprathreshold auditory temporal processing task and a spectro-temporal processing task, both measured under headphones.

Hearing ability of prairie voles (Microtus ochrogaster).

The hearing abilities of mammals are impacted by factors such as social cues, habitat, and physical characteristics. Despite being used commonly to study social behaviors, hearing of the monogamous prairie vole (Microtus ochrogaster) has never been characterized. In this study, anatomical features are measured and auditory brainstem responses (ABRs) are used to measure auditory capabilities of prairie voles, characterizing monaural and binaural hearing and hearing range.

Interaural frequency mismatch jointly modulates neural brainstem binaural interaction and behavioral interaural time difference sensitivity in humans.

The binaural interaction component (BIC) of the auditory brainstem response (ABR) is the difference obtained after subtracting the sum of right and left ear ABRs from binaurally evoked ABRs. The BIC has attracted interest as a biomarker of binaural processing abilities. Best binaural processing is presumed to require spectrally-matched inputs at the two ears, but peripheral pathology and/or impacts of hearing devices can lead to mismatched inputs.

Occluded insertion loss from intracochlear pressure measurements during acoustic shock wave exposure.

Introduction: Injuries to the peripheral auditory system are among the most common results of high intensity impulsive noise exposure. Hearing protection can mitigate this injury, but careful assessment of the insertion loss they provide is necessary. Insertion loss is typically measured using microphone-based acoustic manikins to measure the decrease in sound pressure level transmitted into the ear canal, which precisely measure the change in air conducted sound, but neglect alternate pathways to the inner ear such as bone conduction.

Effects of unilateral eye closure on middle ear muscle contractions.

Middle ear muscle contractions (MEMCs) are most commonly considered a response to high-level acoustic stimuli. However, MEMCs have also been observed in the absence of sound, either as a response to somatosensory stimulation or in concert with other motor activity. The relationship between MEMCs and non-acoustic sources is unclear.

Auditory brainstem development of naked mole-rats ().

Life underground often leads to animals having specialized auditory systems to accommodate the constraints of acoustic transmission in tunnels. Despite living underground, naked mole-rats use a highly vocal communication system, implying that they rely on central auditory processing. However, little is known about these animals' central auditory system, and whether it follows a similar developmental time course as other rodents.

The acoustical effect of the neck frill of the frill-necked lizard (Chlamydosaurus kingii).

Animals localise sound by making use of acoustical cues resulting from space and frequency dependent filtering of sound by the head and body. Sound arrives at each ear at different times, with different intensities, and with varying spectral content, all of which are affected by the animal's head and the relative sound source position. Location cues in mammals benefit from structures (pinnae) that modify these cues and provide information that helps resolve the cone of confusion and provide cues to sound source elevation.

Effects of Varying Laser Parameters During Laser Stapedotomy on Intracochlear Pressures.

Objective: Sensorineural hearing loss is a known complication of stapes surgery. We previously showed that laser stapedotomy can result in intracochlear pressures that are comparable to high sound pressure levels. Optimizing laser settings to those that correspond with the lowest pressure changes may mitigate risk for postoperative hearing loss.

The Binaural Interaction Component in Rhesus Macaques ().

The binaural interaction component (BIC) is a sound-evoked electrophysiological signature of binaural processing in the auditory brainstem that has received attention as a potential biomarker for spatial hearing deficits. Yet the number of trials necessary to evoke the BIC, or its measurability, seems to vary across species: while it is easily measured in small rodents, it has proven to be highly variable and less reliably measured in humans. This has hindered its potential use as a diagnostic tool.

Measurement and Mitigation of Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion.

Hypothesis: High intracochlear pressure transients associated with cochlear implant placement are reduced with smaller, non-styleted arrays, and longer insertion durations.

Background: With increasing focus on hearing preservation during cochlear implant surgery, atraumatic technique is of the utmost importance. Previous studies revealed that high intensity pressure transients can be generated during the insertion of implant electrodes.

Normative Study of the Binaural Interaction Component of the Human Auditory Brainstem Response as a Function of Interaural Time Differences.

Objectives: The binaural interaction component (BIC) of the auditory brainstem response (ABR) is obtained by subtracting the sum of the monaural right and left ear ABRs from the binaurally evoked ABR. The result is a small but prominent negative peak (herein called "DN1"), indicating a smaller binaural than summed ABR, which occurs around the latency of wave V or its roll-off slope. The BIC has been proposed to have diagnostic value as a biomarker of binaural processing abilities; however, there have been conflicting reports regarding the reliability of BIC measures in human subjects.

A comparative study of avian middle ear mechanics.

Sound and hearing play an important role in the lives of many birds, and studies have been published on the acoustic habitat of various species, as well as on various aspects of their hearing system. However the function of the middle ear remains largely unexplored, with existing studies focusing on either single species, or a very narrow range of species. In this article we report measurements of the middle ear transfer function in 39 taxonomically diverse avian species.

Scaling of the avian middle ear.

This article presents a comparative study of morphology of the avian middle ear. The general morphology of the columella shows considerable variation across species, yet few studies have attempted to provide quantitative comparisons, and basic anatomical data has not been thoroughly reported. In this study, we examined the middle ear in 49 taxonomically diverse species of bird.

Characterization of Auditory and Binaural Spatial Hearing in a Fragile X Syndrome Mouse Model.

The auditory brainstem compares sound-evoked excitation and inhibition from both ears to compute sound source location and determine spatial acuity. Although alterations to the anatomy and physiology of the auditory brainstem have been demonstrated in fragile X syndrome (FXS), it is not known whether these changes cause spatial acuity deficits in FXS. To test the hypothesis that FXS-related alterations to brainstem circuits impair spatial hearing abilities, a reflexive prepulse inhibition (PPI) task, with variations in sound (gap, location, masking) as the prepulse stimulus, was used on knock-out mice and B6 controls.

Generalizability of clinically measured acoustic reflexes to brief sounds.

Middle ear muscle contractions (MEMC) can be elicited in response to high-level sounds, and have been used clinically as acoustic reflexes (ARs) during evaluations of auditory system integrity. The results of clinical AR evaluations do not necessarily generalize to different signal types or durations. The purpose of this study was to evaluate the likelihood of observing MEMC in response to brief sound stimuli (tones, recorded gunshots, noise) in adult participants (N = 190) exhibiting clinical ARs and excellent hearing sensitivity.

Risks of Intracochlear Pressures From Laser Stapedotomy.

Hypothesis: Surgical manipulations during laser stapedotomy can produce intracochlear pressure changes comparable to pressures created by high-intensity acoustic stimuli.

Background: New-onset sensorineural hearing loss is a known risk of stapes surgery and may result from pressure changes from laser use or other surgical manipulations. Here, we test the hypothesis that high sound pressure levels are generated in the cochlea during laser stapedotomy.

Characterizing Insertion Pressure Profiles During Cochlear Implantation: Simultaneous Fluoroscopy and Intracochlear Pressure Measurements.

Background: Combined electrical-acoustical stimulation (EAS) has gained popularity as patients with residual hearing are increasingly undergoing cochlear implantation. Preservation of residual hearing correlates with hearing outcomes, but loss of hearing occurs in a subset of these patients. Several mechanisms have been proposed as causing this hearing loss; we have previously described high amplitude pressure transients, equivalent to high-level noise exposures, in the inner ear during electrode insertion.

Establishing an Animal Model of Single-Sided Deafness in .

Objectives: (1) To characterize changes in brainstem neural activity following unilateral deafening in an animal model. (2) To compare brainstem neural activity from unilaterally deafened animals with that of normal-hearing controls.

Study Design: Prospective controlled animal study.